Engine control systems control an engine based on the desired operating mode of the engine. Engine operating modes include, but are not limited to, an OFF mode, an ACCESSORY mode and a RUN mode. In the OFF mode, the engine is not running and the engine control system generates limited control signals. For example, the engine control system may generate a throttle control signal to enable throttle bleed for a short period after transitioning to the OFF mode (i.e., turning the engine off). Additionally, the engine control system may generate a blower control signal to cool the engine for a period during the OFF mode.
Engine control systems may include diagnostic systems to ensure proper operation of some of the components of the engine control system and the integrity of the control signals generated by the engine control system. Traditional engine control systems may generate a false fault status due to improper diagnostic scheduling. For example, an ignition signal diagnostic system monitors a difference between an ignition voltage and a powertrain relay voltage. The ignition signal diagnostic may indicate a false fault status when executed during the period when the engine control system operates the blower to cool the engine in the OFF mode.